Right, it's more complicated because there are different payouts with different odds. But when you add up all the payouts with all the odds it has to add up to >.75.
What I'm objecting to is your idea that machines are more likely to payout after they've lost for a while. Each spin is independent of previous spins. The 75% is just a statistical average over the long run.
The takeout is configurable. With older machines they have to be manually set at the machines, but with more modern machines it is controlled by a server. The period of time while the takeout remains unchanged is referred to as a cycle. Casinos are generally free to change the takeout so long as it is a minimum of the regulated amount. Then there are the regulations requiring idle time at the machines like I mentioned in my previous comment. Additionally, the casino may need to notify the gaming commission prior to making a takeout change depending on local regulations.